Re: GSOS patch?

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <4h3d48$o7s@acme.freenet.columbus.oh.us>,
Dave Althoff <dalloff@freenet.columbus.oh.us> wrote:
> David Empson (dempson@atlantis.actrix.gen.nz) wrote:
> 
> [Slinky RAM cards]
> : The best way of making use of this card would be to set it up as a RAM
> : disk, and use programs which make extensive use of purgeable resources
> : and dynamic segments to keep as much of themselves out of memory as
> : possible.  The program can then be copied to the RAM disk and run from
> : there.
> 
> Hmmm...Would this be a good place to put a cache for disk operations?

That would be possible, as long as the RAM card could be shared safely
with anything else that wanted to use it (e.g. a RAM disk driver).

GS/OS doesn't normally attempt to cache data from files on floppies,
only the directory blocks (unless the program explicitly requests data
caching in the read call).  GS/OS will also free up any cache memory
if it is needed for something else.

A cache in a slinky card would be reasonably fast (not quite as fast
as one in IIgs RAM, because you cannot use the MVN or MVP instructions
to copy data to or from a slinky, and it is limted to 1 MHz).

I can't think of any way in which this could be done, other than
patching GS/OS or the specific driver for the disk drive you wanted to
cache.

> I mean, this is pretty much what you suggest in setting it up as a RAM
> disk...

Not really.  I wasn't suggesting automating the process, just making
the best use of the RAM disk given the existing OS and software.

> I doubt that it would help with a hard drive, but it would be faster
> than floppies... 

It would not help at all with a RamFast.  It might with an Apple SCSI
card, but probably not enough to justify it.

> : If you already have a hard drive, then you gain nothing by doing this.
> 
> Which is why I have 5.25Mb of GS-type RAM, and *no* RAM disk...I mean,
> what good would a RAM disk do me, apart from making my program-running
> space smaller...

I have an 800K RAM disk set up, so I can easily copy a 3.5" disk (e.g.
when running a program that might modify the original disk, and I
don't have a floppy disk handy).  Despite this, I still have nearly 2
MB of free RAM, and I've never run out.

I also find a RAM disk very useful in situations where I _know_ I
don't want to keep a particular file (e.g. the report output by the APW
"Diskcheck" utility).  It saves me having to remember to delete it
from my hard drive.

I'll probably stop using it eventually, if I need the RAM.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand